1. Field of the Invention
This invention relates to a bumper assembly and in particular an assembly for use on motor vehicles in particular cars and vans.
2. Background of the Invention
It is known that automobile bumpers should be designed to withstand small impact forces without damage, or at least minimum damage, occurring at low speeds. Typical low speeds occur during vehicle maneuvering whilst parking. However, modern bumper assemblies must also be capable of offering protection to pedestrians when impacted by a slow moving vehicle.
A known bumper assembly which is claimed to alleviate pedestrian injury is disclosed in GB-A-2322 602 which provides a bumper assembly which comprises a plastic shell mounted on a support rail with the space between the shell and rail being substantially foam filled with different density foams. In one embodiment the upper portion of shell is hollow and collapses on initial impact onto the foam filling which creates an inclined face which is intended to guide a pedestrian onto the bonnet where it is believed that the pedestrian is in less danger of injury.
The present invention provides an improved vehicle bumper with improved guidance for lifting a pedestrian onto the bonnet.
According to the present invention there is provided a bumper assembly comprising a hoop-like support having a central aperture surrounded by an upper beam and lower beam connected by outer portions and which is covered by a resilient shell part, the lower portion of the shell being backed by foam material mounted on the lower beam, with the upper portion of the shell being collapsible onto the upper beam, and a relatively rigid undertray located below and adjacent the lower beam and projecting forwards such that the undertray and foam backed lower portion of the shell provide substantially aligned spaced supports for the lower leg of a pedestrian.
The undertray, lower shell and upper shell may provide progressively decreasing resistance to impact.
The shell is preferably made from a polyolefinic material preferably from a polypropylene based material and may be mounted to the vehicle structure or alternatively may be mounted on the support. The foam is preferably a polyurethane foam which may vary in density, and depth across the width of the lower beam.
The open center of the support allows for a open center bumper assembly which facilitates vehicle engine cooling.
The hoop-like support is preferably formed from a glass fibre reinforced thermoplastics plastics materials and is preferably formed from a polycarbonate based material, for example: XENOY (trademark) available from General Electric. The support may include reinforcing ribs and panels. If necessary the support may include at least one reinforcing rib interconnecting the upper and lower beams. The center portion of the upper beam is preferably set backwards from the front surface of the backing foam on the lower beam such that a line connecting points on the upper beam and said front surface make an angle of inclination to the vertical of at least 12 degrees of arc.
The foam is preferably a hard foam having a density of between 60-80 gm/litre then the angle of inclination is about 12 degrees of arc whereas if the foam is a less dense foam having a density of between 30-45 gm/litre then the angle of inclination may be increased to take account of the deformation of the foam on impact to say 15-20 degrees of arc.
The lower central portion of the shell and foam backing provides a support for said lower leg which is located in use at a height of about 260-270 mm above ground, and the forward portion of the undertray provides a support which is located at about 220-240 mm above the ground, that is about 45 mm below the lower beam support.
The outer portions of the hoop-like support are preferably curved forwards.